1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more particularly, to a mold frame structure of an LCD in which a main frame accommodating an LCD panel and an optical sheet is slim and lightweight and a ground terminal of a PCB attached to the rear side of the main frame is stably grounded.
2. Description of the Related Art
Recently, as technology in the semiconductor industries rapidly develops, slim and lightweight liquid crystal displays (LCDs) having improved performance are produced. Up to now, cathode ray tubes (CRTs) widely used as information display devices have many advantages in view of performance or price. However, CRTs have many disadvantages regarding miniaturization or portability.
On the contrary, LCDs have advantages such as miniaturization, light weight and low power consumption, so that LCDs have gradually attracted attention as an alternative display that can overcome the disadvantages of CRTs. Today, LCDs are actually employed in almost all information processing equipment that require display devices.
In an LCD, a voltage is applied to modify a specific molecular alignment of liquid crystal into another molecular alignment that either blocks or passes light.
Recently, in order to provide competitive products, several slim and lightweight structures have been developed. One of them is a mold frame structure for an LCD. In the mold frame structure of the LCD, optical units, i.e., backlight units are stacked on a display panel including an array substrate and a color filter substrate attached to each other, and accommodated in a main frame so as to protect the resultant structure. Then, a top case and a bottom case are combined with each other.
A printed circuit board (PCB), providing signals to a gate pad and a data pad that are formed at edges of the display panel, is connected to a flexible cable by a taped carrier package (TCP) on which a drive IC is mounted.
FIG. 1 is a perspective view of a general liquid crystal display including elements for a mold frame. An LCD display panel 5 includes an array substrate and a color filter substrate attached to each other. The array substrate has a plurality of pixels formed in a matrix, and the color filter substrate has R, G and B color filters formed in a matrix. A backlight unit is stacked on the LCD display panel. The resultant structure including the LCD display panel and the backlight unit is accommodated in a main frame.
A gate PCB 7, formed at one edge of the display panel 5 to apply a drive signal, is connected to the gate pad of the display panel 5 through a flexible cable, spaced apart from the gate TCP 6a. 
The gate TCP 6a includes a gate drive IC that is arranged in the middle of the flexible cable and controls the drive signal to be applied to the display panel 5 according to a predetermined scan method.
Similarly, a data PCB 9, formed at another edge of the display panel 5 to apply a graphic signal, is connected to the data pad of the display panel 5 through a flexible cable. The data PCB 9 includes a data TCP 6b for applying a signal to the display panel 5 according to a predetermined scan method.
A backlight unit 10 is attached in a stack structure at the back of the display panel 5. The backlight unit 10 includes a plurality of optical sheets 11, a backlight 13 for generating light, a light guide plate 15 for changing the light generated from the backlight into a planar light over the area of the display panel 5, and a reflective plate 17 for reflecting light leaked from the light guide plate 15 to enhance light efficiency.
The backlight unit 10 and the display panel 5 are accommodated in the main frame 21 in a stack structure so as to protect them from an external impact and optically align them. In order to prevent movement of the display panel 5, a panel guide 3 is attached to fix the display panel 5.
The main frame 21 can be made of metal or plastic materials. The display panel 5 and the backlight unit 10 are accommodated in the main frame 21 in a stacked structure and then the panel guide 3 is combined with the main frame 21.
Thereafter, the top case 1 and the bottom case are combined with the main frame 21 accommodating the display panel 5 and the backlight unit 10. With a recent trend to make the LCD thinner, only the top case 1 is combined.
In order to resolve a grounding problem of the gate and data PCBs 7 and 9 folded on a rear side of the main frame 21 by removing the bottom case as described above, a cover plate is attached to the main frame 21 and electrically connected to the PCBs 7 and 9.
FIG. 2 is a plan view of a mold frame of a general liquid crystal display. The display panel and the backlight unit are accommodated in the main frame 21, and the top case is combined with the main frame 21.
The cover plate 23 is attached to the rear side of the main frame 21, and the pad region of the display panel accommodated in the main frame 21, and the PCB (not shown) connected through the TCP are folded on the rear side of the main frame 21.
Additionally, a shield cover 25 covering the PCB is attached providing for electromagnetic interface (EMI) shielding and grounding.
Accordingly, the cover plate 23 attached to the rear side of the main frame 21, the PCB, and the shield cover 25 are arranged in an overlapped form. Screws 26 penetrating an upper end of the shield portion 25 are connected to ground the ground terminals of the PCBs 7 and 9 and the cover plate 23.
The shield cover 25 is attached to cover the PCB by the penetrating screws 26, and the ground terminals of the PCBs arranged between the shield cover 25 and the cover plate 23 are electrically connected to the cover plate 25.
Undesired reference numerals 22a and 22b of FIGS. 1 and 2 represent backlight connectors.
FIG. 3 is a sectional view taken along the line I-I′ of FIG. 2. As shown, the cover plate 23 is attached to the rear side of the main frame (21 in FIG. 2) in order to ground the ground terminals of the PCBs 7 and 9. Additionally, the PCBs 7 and 9 are arranged between the cover plate 23 and the shield cover 25 for shielding the electro-magnetic interface (EMI) generated from the PCBs 7 and 9.
The screws 26 penetrate the shield cover 25 and the PCBs 7 and 9 so as to connect the ground terminals of the PCBs 7 and 9 to the cover plate 23 attached to the rear side of the main frame 21.
The shield cover 25 is used to prevent signals from being distorted due to any external electromagnetic waves and to prevent other modules contained in the LCD from being influenced by electromagnetic waves generated from the PCBs 7 and 9.
However, according to the mold frame of the LCD constructed as described above, the cover plate acting as a ground plate is attached to provide a separate ground of the PCB on the rear side of the main frame, resulting in increased thickness and weight.
Further, the additional process of attaching the cover plate for grounding the ground terminals of the PCBs increases the manufacturing cost and degrades the production efficiency.